(1) Field of the Invention
The present invention relates to a traffic management system, and more particularly to a traffic management system for managing vehicle traffic.
(2) Description of the Related Art
In recent years, attention has been attracted to 5.8 GHz short-range radio communications (DSRC: Dedicated Short-Range Communications) typified by an ETC (Electronic Toll Collection) system which automatically collects tolls from moving vehicles without the need for the vehicles to stop at expressway toll booths. The development of a system of sophisticated networks of roads and vehicles using such short-range radio communications is now in progress.
FIG. 29 of the accompanying drawings shows a conventional road-to-vehicle short-range radio communication system. As shown in FIG. 29, the conventional road-to-vehicle short-range radio communication system has monitor cameras 201, 202 and infrared sensors 211, 212 disposed along a road, a base station 220 disposed near the road, and an information center 230 for managing the entire system.
The information center 230 collects traffic jam information and faulty car information from the monitor cameras 201, 202 and the infrared sensors 211, 212, and analyzes the collected information. The information center 230 sends analytic results to the base station 220, which sends traffic information to those vehicles which are present in its own communication area.
Another conventional short-range radio communication system which has been proposed includes a mobile station, a base station for receiving, via radio communications, information that is representative of an ID of the mobile station, a vehicle type, a present vehicle position, a present time, and a present vehicle speed, a fixed station for receiving the information from the base station through a telephone circuit, and a car navigation unit for providing information contents to measure the present position of the mobile station. The information representing the vehicle position, the vehicle type, the present time, etc. is sent to the fixed station to determine traffic information including a traffic density and a traffic jam. For details, see Japanese laid-open patent publication No. 10-307993, paragraphs 0006 through 0017, FIG. 1, for example.
According to the conventional system shown in FIG. 29, many devices for collecting information, such as monitor cameras for monitoring the road and infrared sensors for monitoring the traffic need to be installed along the road in order to monitor/manage the vehicle traffic situation. Therefore, the entire system is large in scale, a long period of time is required for installing the devices in place, and adjusting the devices after being installed is time-consuming.
The other conventional system disclosed in Japanese laid-open patent publication No. 10-307993 is smaller in scale than the system shown in FIG. 29 because the vehicle as the mobile station and the fixed station communicate with each other to obtain traffic information. However, inasmuch as the vehicle information including the vehicle position and the time information is transmitted from the vehicle to the fixed station, the vehicle has to be equipped with a device of high functionality, such as a car navigation unit for measuring the vehicle position based on GPS, which poses a financial burden on the user of the vehicle. Another problem is that the system does not perform sophisticated traffic management control for predicting the position of a traffic accident and a faulty vehicle and notifying nearby vehicles of the accident information.